This invention relates generally to determining the weight of a load in a bucket of work machine, and more particularly, to determining the weight of a load in a bucket of a work machine having multiple degrees of freedom.
A variety of conventional ways exist to measure the weight of a payload in a bucket of a work machine. Due to the complexity of the process, however, many of these ways contain inherent limitations. For example, some ways are limited to work machines having only 2 degrees of freedom of the bucket, e.g., a front loader. This technique would not be usable on machines having more degrees of freedom, e.g., an excavator. Other ways require the work machine to perform the measurement only while the payload is motionless, or in a given position. This is problematic in that it requires the operator to operate the machine in a way that may add time to each digging cycle. Still other ways require calibration of the measuring system using a known load, or approximate the weight of the payload based on the performance of a different (baseline) machine having a similar configuration, e.g., curve fitting. The former can add unwanted time to the operation of the machine that could otherwise be spent digging, while the latter assumes there is little or no deviation between the work machine and the baseline machine, which is often untrue.
The present invention provides methods and apparatuses for determining a mass of a payload in a work machine. The work machine has a chassis, a cab coupled with the chassis, and a boom coupled with the cab. A first actuator is coupled with the boom and the cab and moves the boom relative to the cab. The work machine has a stick coupled with the boom, and a second actuator coupled with the stick and the boom that moves the stick relative to the boom. The work machine also has a bucket operable to receive the payload. The bucket is coupled with the stick, and a third actuator is coupled with the bucket and the stick and moves the bucket relative to the stick. A first joint angle of the boom relative to the cab is determined at at least two instances in time. A second joint angle of the stick relative to the boom is determined at at least two instances in time. A third joint angle of the bucket relative to the stick is determined at at least two instances in time. A first actuator force exerted on the first actuator is determined at at least two instances in time. A second actuator force exerted on the second actuator is determined at at least two instances in time. A third actuator force exerted on the third actuator is determined at at least two instances in time. A plurality of physical characteristics of the work machine is determined. The mass of the bucket and payload is determined as a function of the first joint angles, the second joint angles, the third joint angles, the first actuator forces, the second actuator forces, the third actuator forces, and the plurality of predetermined physical characteristics.